Author Topic: "TINY" This time a water cooled side shaft version  (Read 4555 times)

Offline gbritnell

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"TINY" This time a water cooled side shaft version
« on: March 12, 2018, 07:24:27 PM »
Gentlemen,
Having got caught up on the model engine repair work I am doing for a friend I thought it about time to start a new project.

 I had posted a thread awhile back asking for some information on how the governor works on a Domestic side shaft engine and thanks to the responses I resolved those issues.

 As with the other "Tiny" engines this one will use the basic dimensions along with some of the same components. I have the drawings finished for all  the conversion parts and the first order of business was to make the helical gears to drive the side shaft/cam disc. Using my helical gear fixture (thanks Chuck) and the Helical gear spread sheet (thanks Don) I made up the cam bushings to cut the gears. My index plates had one row of holes that I could use for the crank gear but I had to drill another row for the shaft gear. To keep the spacing from the crank to the side shaft at a minimum and still have enough meat on the crank gear I came up with 80 DP gears.

 In my vast collection of gear cutters I haven't used this pitch before so I had to make up a gear cutter. I ground a high speed lathe bit to get the needed radius then cut the tooth profile onto a piece of .375 drill rod. This was hardened and tempered due to the tiny size of the teeth.

 The crank gear is 10 teeth with a helical angle of 60 degrees and the side shaft gear is 20 teeth with a helical angle of 30 degrees. The crank gear is steel and the cam gear is brass.
« Last Edit: March 13, 2018, 10:23:16 AM by gbritnell »
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Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #1 on: March 12, 2018, 07:28:19 PM »
 Cutting the 30 degree gear wasn't a problem with my setup (using the helical fixture in my mill vise) but to cut the 60 degree gear I had to mount the fixture onto my angle plate so that I had enough clearance to index the spindle.
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Offline Kim

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Re: "TINY" This time a water cooled side shaft version
« Reply #2 on: March 13, 2018, 02:17:19 AM »
Nice work as always, George.  Those are the cutest little helical gears!
I see how you do it, but I don't think I'll fully grock how you make these gears till I have to get in there and do one myself.
Kim

Online crueby

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Re: "TINY" This time a water cooled side shaft version
« Reply #3 on: March 13, 2018, 02:38:58 AM »
Those gears are great! Was there another thread about that fixture? Looks like another very interesting topic.


 :popcorn:

Online b.lindsey

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Re: "TINY" This time a water cooled side shaft version
« Reply #4 on: March 13, 2018, 11:19:11 AM »
Those look great George!!!  This may be the best "Tiny" yet  :)

Bill

Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #5 on: March 13, 2018, 02:47:36 PM »
Hi Chris,
Here's the link to the original design of the helical gear cutting fixture.
http://www.homemodelenginemachinist.com/showthread.php?p=105973&highlight=helical+gear+cutting+fixture#post105973
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Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #6 on: March 13, 2018, 02:56:37 PM »
Hi Kim,
My previous post covers the whole thread on making and using the helical gear cutting fixture. Somewhere in the archives is a posting by Don Darbonne where he made a spread sheet covering all the facets of the calculations. I believe Marv Klotz also has a program for calculating the gear number.
Basically a fixture is made with a block and spindle to hold the gear blank. At the indexing end is a pair of discs, on fixed to the spindle and the other with the indexing holes. Between the discs and the block is a 1.00"  diameter hub that holds a spiral piece of metal that is formed from flat stock using the calculated numbers for whatever pitch and helix you are going to use. The helical piece of metal rubs against a follower arm with a small ball bearing at the end. As the helical template is rotated against the follower it rotates and advances the spindle thereby cutting a helical path on the gear blank.
gbritnell
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Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #7 on: March 13, 2018, 03:05:51 PM »
 When I built the first "Tiny" I went strictly by the drawing dimensions and after assembly found that the fuel filler tube was cramped by the connecting rod so I extended the crankcase/block to allow more room for the tube. The second thing I changed was more cosmetic and that was to add draft to the water hopper giving it a little more character. On this engine I added a third feature and that is instead of just having a plain flat top on the water hopper I drilled and tapped the corners for 0-80 screws and then made up a cap to simulate a cast water hopper, here again just cosmetic by kind of neat looking.

 The first series of pictures show the block with all the features machined. On the front bottom corner of the cylinder area I have added a boss for the side shaft bearing block.
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Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #8 on: March 13, 2018, 03:10:31 PM »
The next set of pics shows the machined cap, the cap sitting on the block and the cap with the screws in place. The flat head screws were made from aluminum and left on the bar they were turned from. They were then screwed in place and hand tightened. I then used a jewelers saw to cut the screws free from the bar.
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Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #9 on: March 13, 2018, 03:11:52 PM »
This photo shows the screw heads filed flush with the cap.
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Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #10 on: March 13, 2018, 03:13:42 PM »
This set of pics shows all the corners radiused and everything sanded and polished.
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Online b.lindsey

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Re: "TINY" This time a water cooled side shaft version
« Reply #11 on: March 13, 2018, 04:38:23 PM »
Except for the hopper it all looks very familiar :). The hopper does add a very nice touch to it though as does the cast on head "look." Your are moving along quickly George.

Bill

Offline PJPickard

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Re: "TINY" This time a water cooled side shaft version
« Reply #12 on: March 14, 2018, 12:43:52 AM »
Following this one! I have "Tiny" on my build list, but I think I'm going to prefer this!

Love the top of the hopper!

Offline Kim

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Re: "TINY" This time a water cooled side shaft version
« Reply #13 on: March 14, 2018, 04:54:00 AM »
Hi Kim,
My previous post covers the whole thread on making and using the helical gear cutting fixture. Somewhere in the archives is a posting by Don Darbonne where he made a spread sheet covering all the facets of the calculations. I believe Marv Klotz also has a program for calculating the gear number.
Basically a fixture is made with a block and spindle to hold the gear blank. At the indexing end is a pair of discs, on fixed to the spindle and the other with the indexing holes. Between the discs and the block is a 1.00"  diameter hub that holds a spiral piece of metal that is formed from flat stock using the calculated numbers for whatever pitch and helix you are going to use. The helical piece of metal rubs against a follower arm with a small ball bearing at the end. As the helical template is rotated against the follower it rotates and advances the spindle thereby cutting a helical path on the gear blank.
gbritnell
Thanks for the excellent summary George.  I do appreciate it.  I believe I 'mostly' follow it, but I'm just going to have to go through it before I fully get my mind around it.  Thank you for your explanation here!

And your engine is looking great!
Kim

Online Dave Otto

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Re: "TINY" This time a water cooled side shaft version
« Reply #14 on: March 14, 2018, 11:20:23 PM »
That's really cool George, a little tiny side shaft!
I'm looking forward to seeing more of this little beauty.

Dave